Dissolution testing of components of industrial products whose solubility and dissolution rate properties affect product performance can be used as a screening and quality control tool. Solubility properties of solid materials can depend on polymorphic crystalline form, crystal habit, crystal shape, particle size and particle size distribution, and state of solvation. A simple and rapidly performed dissolution test can substitute for the determination of these physical properties by more time consuming and differential thermal analysis, microscopy, etc. The properties instead may be determined with reference to whether they conform to a dissolution rate standard under specified conditions and in relation to a known reference sample of the same material characterized by the above physical properties and possessing the derived dissolution rate and solubility performance.
As noted in U.S. Pat. No. 4,279,860, entitled "Multiple Injector Flow Through Dissolution Cell For Dissolution Testing Apparatus," the broad technique of determining dissolution rate properties is especially of interest in the testing of drug products where the therapeutic performance of drugs is closely related to the drug dissolution properties. Such techniques, for example, can be used as a quality control tool, such as in an in vivo bioequivalency requirement for multisource generic drug products, or as a substitute for human bioavailability testing during the development of new drug product formulations. The principles behind such interest are more fully discussed in the aforementioned U.S. Pat. No. 4,279,860 as well as in U.S. Pat. No. 4,335,438. As noted in such patent and patent application, it is important that the dissolution tests in connection with such uses provide predictive results that are biologically relevant.
While the aforementioned U.S. Pat. No. 4,279,860 discloses and describes a multiple injector flow through dissolution cell for use in such a dissolution testing apparatus which is particularly useful in connection with testing of rapidly dissolving industrial products or drug dosage forms, the dissolution cell disclosed therein is only operative to produce a single sample solution at any given instant, thereby limiting its effectiveness in connection with producing a large number of samples and conducting necessary tests thereon.
As can be appreciated, it is desirable to provide the capability of increasing the rate at which fluid samples may be produced, while at the same time providing for uniformity and repeatability of producing test samples to provide accurate and correct dissolution rate and solubility performance information. Further, it is desirable to provide an apparatus which is not subject to problems associated with cleaning out test cells after samples have been taken, or problems associated with leakage of fluids introduced into the various cells. The present invention achieves these desirable principles in connection with a sampling apparatus so as to provide the capability of providing for a more efficient, quick, uniform and repeatable production of fluid samples, and which is particularly useful in a dissolution testing system.